May be an itenerant frequency for an industrial facility. Could you tell if it was simplex or repeater? Some large industrial complex's will be licensed for many of the itenerant simplex freqs, licensed for a maximuim of two or three watts. But still run a 25 watt mobile on a power supply into a 6 dB antenna. You'll have a dickens trying to figure out who it is, 'cuz users on itenerant frequencies rarely throw out a callsign.